package org.apache.commons.graph.algorithms.visit

import org.apache.commons.graph.Graph

/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements.  See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership.  The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License.  You may obtain a copy of the License at
*
*   http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied.  See the License for the
* specific language governing permissions and limitations
* under the License.
*/

/**
 * Search root node selector.
 *
 * @param <V> the Graph vertices type
 * @param <E> the Graph edges type
 * @param <G> the Graph type
</G></E></V> */
interface VisitSourceSelector<V, E, G : Graph<V, E>> {
    /**
     * Select the root node the search begins from.
     *
     * @param source the root node the search begins from
     * @return the search visit algorithm selector
     */
    fun <S : V> from(source: S): VisitAlgorithmsSelector<V, E, G>
}


/**
 * [VisitSourceSelector] implementation.
 *
 * @param <V> the Graph vertices type
 * @param <E> the Graph edges type
 * @param <G> the Graph type
</G></E></V> */
class DefaultVisitSourceSelector<V, E, G : Graph<V, E>>(private val graph: G) : VisitSourceSelector<V, E, G> {
    /**
     * {@inheritDoc}
     */
    override fun <S : V> from(source: S): VisitAlgorithmsSelector<V, E, G> {
        //var source = source
        //source = Assertions.checkNotNull(source, "Impossible to visit input graph %s with null source", graph)
        require(graph.containsVertex(source)){ "Vertex $source does not exist in the Graph"}
        return DefaultVisitAlgorithmsSelector(graph, source)
    }
}

fun <V, E, G : Graph<V, E>> G.visit(): VisitSourceSelector<V, E, G> = DefaultVisitSourceSelector(this)

fun <V, E, G : Graph<V, E>,S : V> G.visit(source: S) = visit().from(source)